subdomains for default domain with dmarc?

[jeffschips]

Hello. I hope everyone is safe and healthy.

I've noticed in the whm dns zone manager there is not a dmarc entry for sub.maindomain.com, despite that sub.maindomain.com being used and identified in smtp transactions. This was brought to my attention by postmarkapp.com when setting up dmarc email monitoring so as to prevent spoofing, etc. I did notice that in my maindomain.com zone record there is an spf record for both sub.maindomain.com and maindomain.com

Just wondering why and if I should have a corresponding dmarc entry for subdomain.domain.com. I always thought that with these records the subdomain is conflated into the main domain automatically in various internet transactions for the purposes of authenticity.

 

[cPRex]

Hey there! I can confirm that SPF and DKIM pass without a specific entry configured for the subdomain. I didn't have a good way to test the DMARC records on my end, but it would make sense to me that it behaves the same way.

 

[jeffschips]

thanks. I created a single DMARC with ;p=reject;sp=none plus the other values. Unless someone thinks a specific subdomain needs to created I'll assume this is the best way to go. thanks.